1. Field
The present disclosure is directed to wireless communications. More particularly, the present disclosure is directed to a method and apparatus for attaching a remote unit to a mobile core network via a standalone untrusted non-3GPP access network.
2. Introduction
Presently, remote units, such as smartphones, personal computers, tablet computers, connected home devices, smart televisions, set-top boxes communicate with mobile communication networks to send and receive data. Mobile communication networks following the Long Term Evolution (LTE) architecture support several different interfaces between an Access Network (AN) and an Evolved Packet Core (EPC) with different types of access networks use different types of interfaces. For example, the S1 interface is used only between an Evolved Universal Terrestrial Radio Access (E-UTRAN) and EPC. As another example, wireless local area network (WLAN) access to the EPC involves several other interfaces, such as the S2a and STa interfaces for access via trusted WLANs, the SWu and S2b interfaces for access via untrusted WLANs, and the S2c interface for access via either trusted or untrusted WLANs. In addition, new network elements have been specified for WLAN interworking, including the Authentication, Authorization, and Accounting (AAA) server, the Evolved Packet Data Gateway (ePDG), the Trusted Wireless Access Gateway (TWAG), and other network elements. All these different interfaces and network elements for connecting different accesses to EPC have resulted in a complex and difficult to manage architecture.
At times, a WLAN access network is integrated into the E-UTRAN in a way that requires neither new network elements in EPC nor new AN-EPC interfaces, such as by using LTE-WLAN Aggregation (LWA). However, this kind of WLAN integration has limited deployment scenarios because the WLAN access network must always be within the LTE coverage and, more importantly, the WLAN access network needs to be a special WLAN that supports an interface with a mobile communication network base station (eNB) and requires several other enhancements. Such a WLAN access network is not a standalone WLAN because it requires the presence and integration with E-UTRAN. To support interworking with standalone WLAN accesses, which account for a majority of deployment scenarios, additional, WLAN-specific network elements and interfaces are required, which increase the complexity of the system. For example, remote units can access a Next Generation (NextGen) Core Network (NGCN), such as a 5G network, over a non-Third Generation Partnership Project (non-3GPP) access network, such as a WLAN access network. To access the NGCN, a remote unit must use a specific protocol, such as a Non-Access Stratum (NAS) protocol.